Non-aqueous electrolyte secondary battery comprising composite particles

ABSTRACT

The present invention relates to a non-aqueous electrolyte secondary battery. The negative electrode of the present invention is characterized by its composite particles constructed in such a manner that at least part of the surrounding surface of nuclear particles containing at least one of tin, silicon and zinc as a constituent element, is coated with a solid solution or an intermetallic compound, which are composed of the element contained in the nuclear particles, and at least one other element except the elements contained in the nuclear particles selected from a group comprising group 2 elements, transition elements, group 12 elements, group 13 elements and group 14 elements except carbon of the Periodic Table. The electrolyte uses anion lithium salts of organic acid dissolved in organic solvent with high oxidation resistant characteristics. By adopting the above construction, a battery which generates only a small amount of gas during a high temperature storing can be obtained. Furthermore, the batteries enjoy high energy density and a lower reduction rate of discharge capacity when used repeatedly as well as high charge/discharge properties.

This Application is a U.S. National Phase Application of PCTInternational Application No. PCT/JP99/06689, filed Nov. 30, 1999. Thisapplication is a continuation-in-part of U.S. application Ser. No.09/090,484, filed Jun. 3, 1998, now U.S. Pat. No. 6,090,505 issued Jul.18, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to a non-aqueous electrolyte secondarybattery (hereinafter, battery), and especially relates to batterieswhose electrochemical properties such as the charge/discharge capacityand charge/discharge cycle life have been enhanced by improvements innegative electrode materials, and solvents used for the non-aqueouselectrolytes.

In recent years, lithium secondary batteries with non-aqueouselectrolytes, which are used in such fields as mobile communicationsdevices including portable information terminals and portable electronicdevices, main power sources of portable electronic devices, small sizedomestic portable electricity storing devices, motor cycles using anelectric motor as a driving source, electric cars and hybrid electriccars, have characteristics of a high electromotive force and a highenergy density.

When lithium metal with a high capacity is used as a negative electrodematerial, dendritic deposits are formed on the negative electrode duringcharging. Over repeated charging and discharging, these dendriticdeposits penetrate through separators and polymer gel electrolytes tothe positive electrode side, causing an internal short circuit. Duringdischarging, these dendritic deposits break, falling from the surface ofthe bulk lithium-metal negative electrode, thus forming “dead” lithiumwhich does not contribute to charge/discharge reaction. Furthermore,reaction activity of the deposited lithium is high since they have alarge specific surface area. Due to this, the lithium reacts withsolvents in the electrolytic solution on their surfaces, and form asurface film similar to a solid electrolyte which has no electronicconductivity. This increases the internal resistance of the batteries,causing some particles to be excluded from the network of the electronicconduction, thereby lowering the charge/discharge efficiency of thebattery. For these reasons, the lithium secondary batteries usinglithium metal as a negative electrode material have a low reliabilityand a short cycle life.

To suppress the formation of such dendrites, it has been proposed thatlithium alloys such as a lithium-aluminum alloy and a wood's alloy areused instead of lithium metal. Metals capable of forming alloys withlithium and alloys containing at least one such metal can be used as anegative electrode material with a relatively high electrochemicalcapacity in the initial charge/discharge cycle. However, by repeatedlyalloying with and deintercalating lithium, they may undergo a phasechange even when the crystal structure of the original alloy ismaintained, or sometimes, the crystal structure of the alloy itselfchanges.

In this case, particles of the metal or an alloy which are hostmaterials of the lithium (active material), swell and shrink. As thecharge/discharge cycle proceeds, crystal grains are stressed andcracked, thus particles are pulverized and leave off from the electrodeplate. As the particles are pulverized, grain boundary resistance andcontact resistance of the grain boundaries increase. As a result,resistance polarization during charging and discharging increases. Thus,when charging is conducted at a controlled voltage level, charging depthbecomes shallow, limiting the amount of charged electricity in thebattery. On the other hand, during discharging, the voltage level isdecreased by the resistance polarization, reaching thedischarge-termination voltage early. Thus, superior charge/dischargecapacity and cycle properties are difficult to achieve.

Nowadays, lithium secondary batteries which use, as a negative electrodematerial, carbon materials capable of intercalating and deintercalatinglithium ions, are commercially available. In general, lithium metal doesnot deposit on carbon negative electrodes. Thus, short circuits are notcaused by dendrites. However, the theoretical capacity of graphite whichis one of the currently used carbon materials is 372 mAh/g, only onetenth of that of pure Li metal.

Other active material compounds include diniobium pentaoxide (Nb₂O₅),titanium disulfide (TiS₂), molybdenum dioxide (MoO₂), lithium titanate(Li₄/₃Ti₅/₃O₄). In the case of these materials, lithium is ionized andmaintained among the host substances. Due to this, compared with lithiummetal whose chemical activity is high, these materials are chemicallystable, do not form dendritic deposits, and contribute to higher cycleproperties. Among them, some carbon materials are alreadycommercialized.

Other known, negative electrode materials include pure metallicmaterials and pure non-metallic materials which form composites withlithium. For example, composition formulae of compounds of tin(Sn),silicon (Si) and zinc (Zn) with the maximum amount of lithium arerespectively Li₂₂Sn₅, Li₂₂Si₅, and LiZn. Within the range of thesecomposition formulae, metallic lithium does not normally deposit. Thus,an internal short circuit is not caused by dendrites. Furthermore, theelectrochemical capacities between these compounds and each elementmentioned above are respectively 993 mAh/g, 4199 mAh/g and 410 mAh/g;all are larger than the theoretical capacity of graphite.

As other compound negative electrode materials, the Japanese PatentLaid-Open Publication No. H07-240201 discloses a non-metallic silicidecomprising transition elements. The Japanese Patent Laid-OpenPublication No. H09-63651 discloses negative electrode materials whichare made of inter-metallic compounds comprising at least one of group 4Belements, P and Sb, and have a crystal structure of one of the CaF2type, the ZnS type and the AlLiSi type.

As a solvent of the electrolyte of the battery, cyclic carbonates suchas propylene carbonate and ethylene carbonate, acyclic carbonates suchas diethyl carbonate, and dimethyl carbonate, cyclic carboxylate such asgamma-butyrolactone and gamma-valerolactone, acyclic ethers such asdimethoxy ethane and 1,3-dimethoxy propane, and cyclic ethers such astetrahydrofuran and 1,3-dioxolane are widely used.

It is desirable to adopt electrolyte with high electrical conductivityto the batteries. Due to this, solvents with a high dielectric constantand a low viscosity are preferably used. However, being high in thedielectric constant simply means high in polarity, in other words, highin viscosity. Therefore, among the electrolytes mentioned above,solvents with high dielectric constant such as propylene carbonate(dielectric constant ∈=65) and solvents with low dielectric constantsuch as 1,2-dimethoxy ethane (∈=7.2) are often mixed and used.

The electrolyte used in the non-aqueous electrolyte batteries alsocontain supporting electrolytes dissolved in the solvents mentionedabove at a concentration of about 1 mol. The supporting electrolytesinclude anion lithium salts of inorganic acid such as lithiumperchlorate, lithium borofluorides and lithium phosphofluoride, andanion lithium salts of organic acid such as trifluoromethane sulfonicacid lithium and bis-trifluoromethane sulfonic acid imido lithium.

But, the above high capacity negative electrode materials includefollowing problems.

Negative electrode materials of pure metallic materials and purenon-metallic materials which form compounds with lithium have inferiorcharge/discharge cycle properties compared with carbon negativeelectrode materials. The reason for this is assumed to be thedestruction of the negative electrode materials caused by their volumeexpansion and shrinkage.

On the other hand, as negative electrode materials with an improvedcycle life property unlike the foregoing pure materials, the JapanesePatent Laid-Open Publication No. H07-240201 and the Japanese PatentLaid-Open Publication No. H09-63651 respectively disclose non-metallicsilicides composed of transition elements and intermetallic compoundswhich are composed of at least one of group 4B elements, P and Sb, andhave a crystal structure of one of the CaF2 type, the ZnS type and theAlLiSi type.

Batteries using the negative electrode materials comprising thenon-metallic silicides composed of transition elements are disclosed inthe Japanese Patent Laid-Open Publication No. H07-240201. The capacitiesof the embodiments of the invention and a comparative example at thefirst cycle, the fiftieth cycle and the hundredth cycle suggest that thebatteries of the invention have improved charge/discharge cycleproperties compared with lithium metal negative electrode materials.However, when compared with a negative electrode material of naturalgraphite, the increase in the capacity of the battery is only about 12%.

The materials disclosed in the Japanese Patent Laid-Open Publication No.H09-63651 have a better charge/discharge cycle property than a Li-Pballoy negative electrode material according to an embodiment and acomparative example. The materials also have a larger capacity comparedwith a graphite negative electrode material. However, the dischargecapacity decreases significantly up to the 10-20th charge/dischargecycles. Even when Mg₂Sn, which is considered to be better than any ofthe other materials, is used, the discharge capacity decreases toapproximately 70% of the initial capacity after about the 20th cycle.Thus, their charge/discharge properties are inferior.

When lithium metal is used as a negative electrode, the electrolyte,which is in contact with the negative electrode, and is exposed to anextremely high reduction atmosphere, tends to react with the lithiummetal, and is consequently reduced, and decomposed. Regarding lithiumalloys, when those predominantly composed of lithium are used in thenegative electrode, the potential of the negative electrode becomesalmost same as that of lithium metal, thus reduction and decompositionof the electrolyte occur in the same manner as the lithium metal.Furthermore, as mentioned earlier, the negative active materials getpulverized over repeated charges and discharges, and inevitably fall offfrom the electrode plate.

In the case of the alloys whose main constituent metal is not lithium,the potential of the negative electrode becomes noble compared withlithium metal or the foregoing lithium alloys. Thus, the electrolyte,which could be reduced and decomposed when contacting the foregoinglithium alloys, can be used. However, compared with the foregoinglithium alloys, these alloys whose main constituent metal is not lithiumare hard and brittle, and thus get pulverized significantly, andinevitably fall off from the electrode plate.

If currently used solvents such as ethylene carbonate, dimethylcarbonate, diethyl carbonate, ethylmethyl carbonate, propylenecarbonate, gamma-butyrolactone, and gamma-valerolactone are adopted fora system in which lithium metal or a lithium alloy is used in a negativeelectrode, the electrolyte may decompose and gas may be produced whenthe battery is charged and stored at high temperatures. Moreover, if thebattery is repeatedly charged and discharged, parallel to thecharge/discharge reaction in the negative electrode, the electrolyte isgasified, lowering the charge/discharge efficiency, resulting indecreased cycle properties.

When graphite-group carbon materials are used as a negative electrodematerial, and propylene carbonate is adopted for an electrolyticsolution, the electrolyte decomposes at potentials more noble than thatof lithium metal. Consequently, lithium ions are not intercalatedbetween layers of graphite, thus the battery does not function.Considering these points, currently commercialized lithium secondarybatteries with the graphite used for negative electrode materialsfrequently use electrolyte containing ethylene carbonate. However, themelting point of ethylene carbonate is 37° C. higher than roomtemperature. Therefore, at low temperatures, ionic conductivity of theelectrolyte for lithium ions plummets, lowering charge/dischargepriorities.

When inorganic compound materials such as titanium disulfide are used asa negative electrode active material, intercalation and de-intercalationof lithium occur at sufficiently noble potentials compared with lithiummetal and lithium alloys. Thus, even when the negative electrode activematerials come into contact with the electrolyte, reductiondecomposition does not occur. Moreover, even when propylene carbonate isused for the electrolytic solution, intercalation and de-intercalationare not impeded by decomposition as it is the case with the graphitematerials, therefore, a wider range of electrolytes are applicable.However, potentials of the negative electrode using the foregoinginorganic compound materials is noble, causing battery voltage toinevitably become low. This is a disadvantage of achieving higher energydensity.

Regarding the supporting electrolytes, the thermal stability of lithiumperchlorate, lithium borofluorides and lithium fluorophosphate needs tobe improved. Furthermore, fluorine-containing inorganic anion saltscontained in the forgoing compounds react with trace amounts of watercontained in an electrolyte and decompose.

The present invention aims to address the forgoing problems ofconventional batteries.

BRIEF SUMMARY OF THE INVENTION

The negative electrode of the batteries of the present invention ischaracterized by its main material which uses composite particlesconstructed in such a manner that at least part of the surroundingsurface of nuclear particles containing at least one of tin, silicon andzinc as a constituent element, is coated with a solid solution or aninter-metallic compound composed of an element contained in the nuclearparticles and at least one element (exclusive of the elements containedin the nuclear particles) selected from a group comprising group 2elements, transition elements, group 12 elements, group 13 elements andgroup 14 elements (exclusive of carbon) of the Periodic Table.

Further, the solvents of the electrolyte of the batteries of the presentinvention include at least one compound selected from a group comprisingethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethylcarbonate, propylene carbonate, gamma-butyrolactone andgamma-valerolactone.

Moreover, the supporting electrolytes in the electrolyte of thebatteries of the present invention includes at least one compoundselected from a group comprising bis-trifluoromethane sulfonic acidimido lithium, bis-pentafluoro ethane sulfonic acid imido lithium,bis(1,2-benzene diolate(2-)-O,O′)lithium borate, bis(2,3-naphthalenediolate(2-)-O,O′)lithium borate, bis(2,2′-biphenyldiolate(2-)-O,O′)lithium borate, and bis(5-fluoro-2-olate-1-benzenesulfonic acid-O,O′)lithium borate.

The foregoing construction provides batteries which rarely suffergeneration of gas when stored at high temperatures. Moreover, even whenthe batteries are repeatedly charged and discharged, charge/dischargeefficiency of their negative electrode does not decrease. The batteriescan be used in a wide range of temperatures. Furthermore, the batteriesenjoy high energy density, maintain discharge capacity well overrepeated use as well as high charge/discharge properties.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary as well as the following Detailed Description ofPreferred Embodiments of the Invention, will be better understood whenread in conjunction with the appended drawing. For the purpose ofillustrating the invention, there is shown in the drawing, an embodimentwhich is presently preferred. It should be understood, however, that theinvention is not limited to the precise arrangements andinstrumentalities shown.

FIG. 1 shows a vertical cross section of a cylindrical battery of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The batteries of the present invention comprise positive and negativeelectrodes capable of intercalating and de-intercalating lithium, anon-aqueous electrolytic solution and separators or solid electrolytes.

As a negative electrode material used in the present invention,composite particles whose nuclear particles composed of solid phase Aare coated with solid phase B over the whole surface or part of thesurface, are used. The solid phase A contains at least one of tin,silicon and zinc as a constituent element. The solid phase B is composedof a solid solution or inter-metallic compounds composed of at least oneof tin, silicon and zinc and at least one element (exclusive of theforegoing constituent elements) selected from a group comprising group 2elements, transition elements, group 12 elements, group 13 elements andgroup 14 elements (exclusive of carbon) of the Periodic Table.Hereinafter, the foregoing negative electrode materials are called“composite particles”. When the composite particles are used as anegative electrode material, the solid phase B helps to suppressexpansion and shrinkage of the solid phase A caused by charging anddischarging, thereby achieving a negative electrode material withsuperior charge/discharge cycle properties.

It can be considered that the solid phase A of the negative electrodematerial of the present invention mainly contributes to a highercharge/discharge capacity since it contains at least one of Sn, Si andZn, and the solid phase B which coats the whole or part of thesurrounding surface of the nuclear particles comprising the solid phaseA, contributes to improvement of the charge/discharge cycle properties.The amount of lithium contained in the solid phase B is normally lessthan that contained in metal, a solid solution or an inter-metalliccompound.

In other words, the negative electrode material used in the presentinvention is constructed such that particles, which contain at least oneof high-capacity Sn, Si and Zn as a constituent element, are coated withthe solid solution or the inter-metallic compounds which are resistantto pulverization. The solid solution or the inter-metallic compound inthe coating layer prevents significant changes in crystal structure,namely changes in volume of the nuclear particles caused byelectrochemical intercalating and deintercalating of lithium. In thismanner, pulverization of nuclear particles is restricted.

Further, within the composite particles, only the solid phase B, whichdoes not contain so much of active lithium, comes in contact with theelectrolyte. Therefore, even when the solid phase B is in contact withthe electrolyte, the electrolyte does not decompose easily. The solventsand supporting electrolytes of the electrolyte are highly stable againstheat, and also stable against water contained in the electrolyte. Thus,it is thought when the battery is stored at high temperatures, gas israrely generated.

The method of manufacturing composite particles used in the negativeelectrode is described in the followings.

In one manufacturing method of the composite materials, a fused mixtureof elements contained in the composite particles at a predeterminedcomposition ratio is quenched and solidified by dry-spraying,wet-spraying, roll-quenching or turning-electrode method. The solidifiedmaterial is heat treated at a temperature lower than the solid linetemperature of a solid solution or intermetallic compounds. The solidline temperature is determined by the composition ratio. The quenchingand solidifying of the fused mixture allows the solid phase A to depositas a nucleus of a particle, and at the same time, allows the solid phaseB, which coats part of or the whole surface of the solid phase A, todeposit. The following heat treatment enhances evenness of the solidphase A and the solid phase B. Even when the heat treatment is notconducted, composite particles suitable for the present invention can beobtained. Apart from the quenching method mentioned above, other methodsare applicable providing they can quench the fused mixture rapidly andadequately.

In another manufacturing method, a layer of deposits comprisingessential elements in forming solid phase B is formed on the surface ofthe powder of the solid phase A. The layer is treated at temperatureslower than the solid phase line. This heat treatment allows constituentelements within the solid phase A to disperse throughout the depositlayer to form the solid phase B as a coating layer. The deposit layercan be formed by plating or by a mechanical alloying method. In the caseof the mechanical alloying method, the heat treatment is not alwaysnecessary. Other methods can also be used on the condition that they canform the deposit layer.

As a conductive material for the negative electrode, any electronicconductive materials can be used. Examples of such materials includegraphite materials including natural graphite (scale-like graphite)synthetic graphite and expanding graphite; carbon black materials suchas acetylene black, highly structured furnace black, channel black,furnace black, lamp black and thermal black; conductive fibers such ascarbon fibers and metallic fibers; metal powders such as copper andnickel; and organic conductive materials such as polyphenylenederivatives. These materials can be used independently or incombination. Among these conductive materials, synthetic graphite,acetylene black and carbon fibers are especially favorable.

The total amount of the additives is not specifically defined, however,1-50 wt %, especially 1-30% of the negative electrode materials isdesirable. As negative electrode materials (composite particles) of thepresent invention are themselves conductive, even if conductivematerials are not added, the battery can still actually function.Therefore, the battery has more room available to contain compositeparticles.

Binders for the negative electrode can be either thermoplastic resin orthermosetting resin. Desirable binders for the present inventionincludes the following materials; polyethylene, polypropylene,polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF),styrene-butadiene rubber, a tetrafluoroethylene-hexafluoropropylenecopolymer (FEP), a tetrafluoroethylene-perfluoroalkyl vynyl ethercopolymer (PFA), a vinyliden fluoride-hexafluoropropylene copolymer, avinyliden fluoride-chlorotrifluoroethylene copolymer, aethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), a vinylidenfluoride-pentafluoropropylene copolymer, a propylene-tetrafluoroethylenecopolymer, a ethylene-chlorotrifluoroethylene copolymer (ECTFE), avinyliden fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, avinyliden fluoride perfluoromethyl vinyl ether-tetrafluoroethylenecopolymer, an ethylene-acrylic acid copolymer or its Na+ ioncrosslinking body, an ethylene-methacrylic acid copolymer or its Na+ ioncrosslinking body, a methyl acrylate copolymer or its Na+ ioncrosslinking body, and an ethylene methyl methacrylate copolymer or itsNa+ ion crosslinking body. Favorable materials among these materials arestyrene butadiene rubber, polyvinylidene fluoride, an ethylene-acrylicacid copolymer or its Na+ ion crosslinking body, an ethylene-methacrylicacid copolymer or its Na+ ion crosslinking body, a methyl acrylatecopolymer or its Na+ ion crosslinking body, and an ethylene methylmethacrylate copolymer or its Na+ ion crosslinking body.

As a current collector for the negative electrode, any electronicconductor can be used on the condition that it does not chemicallychange in the battery. For example, stainless steel, nickel, copper,titanium, carbon, conductive resin, as well as copper and stainlesssteel whose surfaces are coated with carbon, nickel or titanium can beused. Especially favorable materials are copper and copper alloys.Surfaces of these materials can be oxidized. It is desirable to treatthe surface of the current collector to make it uneven. Usable forms ofthe foregoing materials as the current collector include a foil, a film,a sheet, a mesh sheet, a punched sheet, a lath form, a porous form, afoamed form and a fibrous form. The thickness is not specificallydefined however, normally those of 1-500 μm in thickness are used.

As positive electrode active materials, lithium compounds or non-lithiumcontaining compounds can be used. Such compounds include Li_(x)CoO₂,Li_(x)NiO₂, Li_(x)MnO₂, Li_(x)Co_(y)Ni_(1−y)O₂,Li_(x)Co_(y)M_(1−y)O_(z), Li_(x)Ni_(1−y)M_(y)O_(z), Li_(x)Mn₂O₄,Li_(x)Mn_(2−y)M_(y)O₄ (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co,Ni, Cu, Zn, Al, Cr, Pb, Sb and B, and x=0-1, Y=0-0.9, z=2.0-2.3). Thevalue of x is the value before charging and discharging, thus it changesalong with charging and discharging. Other usable positive electrodematerials include transition metal chalcogenides, a vanadium oxide andits lithium compounds, a niobium oxide and its lithium compounds, aconjugate polymer using organic conductive materials, and shevril phasecompounds. It is also possible to use a plurality of different positiveelectrode materials in a combined form. The average diameter ofparticles of the positive electrode active materials is not specificallydefined, however desirably it is 1-30 μm.

Conductive materials for the positive electrode can be any electronicconduction material on the condition that it does not chemically changewithin the range of charge and discharge electrical potentials of thepositive electrode materials in use. Examples of such materials includegraphite materials including natural graphite (scale-like graphite) andsynthetic graphite; carbon black materials such as acetylene black,highly structured furnace black, channel black, furnace black, lampblack and thermal black; conductive fibers such as carbon fibers andmetallic fibers; fluorinated carbon; metal powders such as aluminum;conductive whiskers such as a zinc oxide and potassium titanate,conductive metal oxides such as a titanium oxide, and organic conductivematerials such as polyphenylene derivatives. These materials can be usedindependently or in combination. Among these conductive materials,synthetic graphite and acetylene black are especially favorable.

The total amount of the conductive materials to be added is notspecifically defined, however, 1-50 wt %, especially 1-30% of thepositive electrode materials is desirable. In the case of carbon andgraphite, 2-15 wt % is especially favorable.

Binders for the positive electrode can be either thermoplastic resin orthermosetting resin. The binders for the negative electrode mentionedearlier can be used effectively, however, PVDF and PTFE are morepreferable.

Current collectors for the positive electrode of the present inventioncan be any electronic conductive materials on the condition that it doesnot chemically change within the range of charge and discharge electricpotentials of the positive electrode materials in use. For example, thecurrent collectors for the negative electrode mentioned earlier can beused effectively. The thickness of the current collectors is notspecifically defined, however, those of 1-500 μm in thickness are used.

As electrode mixtures for the positive electrode and the negativeelectrode plates, conductive materials, binders, fillers, dispersants,ionic conductors, pressure enhancers, and other additives can be used.Any fiber material, which does not change chemically in the battery, canbe used as fillers. In general, fibers of olefin polymers such aspolypropylene and polyethylene, and fibers such as glass and carbon areused as fillers. The amount of the filler to be added is notspecifically defined however, it is desirably b 0-30 wt % of theelectrode binders.

As for the construction of the positive electrode and the negativeelectrode, it is favorable that at least the surfaces of the negativeelectrode and the positive electrode where there are the electrodemixtures are facing each other.

The non-aqueous electrolytes of the present invention are formed bydissolving anionic lithium salts of organic acid in non-aqueous solventswith a high oxidation resistance.

Examples of non-aqueous solvents include cyclic carbonates such asethylene carbonate (EC), propylene carbonate (PC), butylene carbonate(BC), and vinylene carbonate (VC); acyclic carbonates such as dimethylcarbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC),and dipropyl carbonate (DPC); aliphatic carboxylates such as methylformate, methyl acetate, methyl propionate, and ethyl propionate;gamma-lactones such as gamma-butyrolactone (GBL) andgamma-valerolactone; acyclic ethers such as 1,2-dimethoxy ethane (DME),1,2-diethoxy ethane (DEE), and ethoxy methoxy ethane (EME); cyclicethers such as tetrahydrofuran and 2-methyl tetrahydrofuran; andnon-protonic organic solvents such as dimethyl sulfoxide, 1,3-dioxolane,formamide, acetamide, dimethylformamide, dioxolane, acetonitrile,propylnitrile, nitromethane, ethyl monoglime, triester phosphoric acid,trimethoxymethyne, dioxolane derivatives, sulfolane, methylsulfolane,1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylenecarbonate derivatives, tetrahydrofuran derivatives, ethyl ether,1,3-propane saltone, anisole, dimethyl sulfoxide and N-methyl pyrolidon,These solvents are used independently or as a mixture of two or moresolvents. Mixtures of cyclic carbonate and acyclic carbonate, or cycliccarbonate, acyclic carbonate and aliphatic carboxylate are especiallyfavorable.

Among these solvents, as solvents having high oxidation resistance, EC,DMC, DEC, EMC, PC, GBL and gamma-valero lactone are preferable.

Conventionally, it has been difficult to adopt PC for lithium ionsecondary batteries using graphite materials which are widely used,since PC decomposes when it comes into contact with electrodes. It hasalso been difficult to use GBL and gamma-valero lactone for electrolyteof the batteries using lithium metal or lithium alloys in the negativeelectrodes since reduction decomposition potentials of these solventsare more noble than the potentials of the electrodes made from theforegoing materials. However, when the composite particles of thepresent invention are used for the negative electrode, GBL andgamma-valero lactone can be used without leading to decomposition of theelectrolyte since the electrode potential using the composite particlesbecomes more noble than reduction decomposition potentials of thesesolvents. Further, PC, GBL and gamma-valero lactone have high dielectricconstant, in other words, a high viscosity. Due to this high-viscosity,should the composite particles be fragmented, they would not come offfrom the electrode plate so easily.

When solvents such as EC, DMC, DEC, EMC, PC, GBL and gamma-valerolactone are adopted for a system in which lithium metal or a lithiumalloy is used in a negative electrode, the electrolyte may decompose andgas may be produced when the battery is charged and stored at hightemperatures. Moreover, if the battery is repeatedly charged anddischarged, parallel to the charge/discharge reaction of the negativeelectrode, the electrolyte is gasified, lowering the charge/dischargeefficiency, resulting in decreased cycle properties. However, thecomposite particles of the present invention do not react with theelectrolytes in such a manner.

Lithium salts which dissolve into the foregoing solvents include LiClO₄,LiBF_(4,), LiPF₆, LiAlCl₄, LiSbF₆, LiSCN, LiCl, LiCF₃SO₃, LiCF₃CO₂,Li(CF₃SO₂)₂, LiAsF₆, LiN(CF₃SO₂)₂, LiB₁₀Cl₁₀, lithium salts of loweraliphatic carboxylic acid, LiCl, LiBr, LiI, chloroborane lithium,4-phenil boric acid, borates such as bis(1,2-benzenediolate(2-)-O,O′)lithium borate, bis(2,3-naphthalenediolate(2-)-O,O′)lithium borate, bis(2,2′-biphenyldiolate(2-)-O,O′)lithium borate, and bis(5-fluoro-2-olate-1-benzenesulfonic acid-O,O′)lithium borate, and imido salts such asbis-trifluoromethane sulfonic acid imido lithium((CF₃SO₂)₂NLi), andbis-pentafluoroethane sulfonic acid imido lithium((C₂F₅SO₂)₂NLi). Theselithium salts can be used individually or in mixture of two or more inan electrolyte.

Among these lithium salts, especially anion lithium salts of organicacid are superior to inorganic acid anion lithium salts such as lithiumperchlorate and lithium fluorophosphate in terms of thermal stability.Due to this, these supporting electrolytes do not thermally decompose tolower the properties of the battery, even when used or stored at hightemperatures, thus, are preferably used.

Anion lithium salts of organic acid preferably include at least onecompound selected from a group comprising (CF₃SO₂)₂NLi, (C₂F₅SO₂)₂NLi,bis(1,2-benzene diolate(2-)-O,O′)lithium borate, bis(2,3-naphthalenediolate(2-)-O,O′)lithium borate, bis(2,2′-biphenyldiolate(2-)-O,O′)lithium borate, and bis(5-fluoro-2-olate-1-benzenesulfonic acid -O,O′)lithium borate.

The reduction decomposition withstanding voltage and the oxidationdecomposition withstanding voltage of (CF₃SO₂)₂NLi on a platinumelectrode are respectively 0V and 4.7V against a lithium referenceelectrode. Similarly, those voltages of (C₂F₅SO₂₎ ₂ NLi on a platinumelectrode are respectively 0V and 4.7V, bis(5-fluoro-2-olate-1-benzenesulfonic acid-O,O′)lithium borate, 0V and 4.5V, and bis(2,2′-biphenyldiolate(2-)-O,O′)lithium borate, 0V and 4.1V or higher.

Therefore, these anion lithium salts of organic acid can be preferablyused to enhance the energy density of the lithium secondary batteries.

On the other hand, the reduction decomposition withstanding voltage andoxidation decomposition withstand voltage of bis(1,2-benzenediolate(2-)-O,O′)lithium borate on a platinum electrode are respectively0V and 3.6V against a lithium reference electrode, and those ofbis(2,3-naphthalene diolate(2-)-O,O′)lithium borate on a platinumelectrode are 0V and 3.8V. If an electrolyte, in which these supportingelectrolytes are dissolved, is used for an active material such aslithium cobaltate, lithium nickelate and lithium manganate whichgenerates a high voltage of not less than 4V against a lithium referenceelectrode, the supporting electrolytes decompose. However, transitionmetal sulfides, whose electromotive force is about 3V against a lithiumreference electrode such as lithium-titanium disulfide (LiTiS₂) andlithium-molybdenum sulfide (LiMoS₂), can be used in these potentialregions.

The amount of the electrolyte to be added to the battery is notspecifically defined. Considering the amount of the positive electrodeand the negative electrode materials and the size of the battery,required amount can simply be used. The amount of the supportingelectrolytes to be dissolved against the non-aqueous electrolytes is notspecifically defined, however, 0.2-2 mol/l, especially 0.5-1.5 mol/l arepreferable.

It is effective to add other compounds to the electrolyte in order toimprove discharge and charge/discharge properties. Such compoundsinclude triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glaim, pyridine, triamide hexaphosphate, nitrobenzenedirevatives, crown ethers, quaternary ammonium salt, and ethylene glycoldialkyl ether.

As a separator of the present invention, insulating thin films with finepores, which have a large ion permeability and a predeterminedmechanical strength, are used. It is desirable that the pores of theseparators close at or above a predetermined temperature to increaseresistance. For an organic solvent resistance and a hydrophobicproperty, olefin polymers including polypropylene and polyethylene canbe used individually or in combination. Sheets, non-wovens and wovensmade with glass fiber can also be used. The diameter of the fine poresof the separators is desirably set within the range through whichpositive electrode and negative electrode materials, binding materials,and conductive materials separated from electrode sheets can notpenetrate. A desirable diameter is, for example, 0.01-1 μm. Thethickness of the separator is generally 10-300 μm. The porosity isdetermined by the permeability of electrons and ions, material andmembrane pressure, in general however, it is desirably 30-80%.

It is also possible to construct a battery such that polymer materials,which absorb and retain an organic electrolyte comprising solvents andlithium salts soluble in the solvents, are included in the electrodemixtures of the positive and negative electrodes, and porous separators,which comprise polymers capable of absorbing and retaining the organicelectrolyte, are formed integrally with the positive and the negativeelectrode. As the polymer materials, any materials capable of absorbingand retaining organic electrolytes can be adopted. Among such materials,a copolymer of vinylidene fluoride and hexafluoro propylene isespecially favorable.

The following is a detailed description of the materials used in thebatteries of the present invention.

The positive electrode and the negative electrode of the battery of thepresent invention are constructed such that a current collector iscoated with a mixture layer which includes the positive electrode activematerials and the negative electrode materials capable ofelectrochemically and reversibly intercalating and de-intercalatinglithium ions as main constituents, and conductive materials as well asbinders.

(Manufacture of the Composite Particles)

In Table 1, components (pure elements, inter-metallic compounds, solidsolution) of the solid phase A and the solid phase B of the compositeparticles used in the preferred embodiments of the present invention,composition ratios of elements, fusion temperatures, and solid phaseline temperatures are shown. Commercially available highly pure reagentsare used as materials for each element.

To obtain solid materials, powder or a block of each element containedin the composite particles is put into a fusion vessel in thecomposition ratio shown in Table 1, and fused at the temperature alsoshown in Table 1. The fused mixture is quenched by the roll-quenchingmethod and solidified to form a solid material which is then heattreated at temperatures of 10° C.-50° C. lower temperature than thesolid phase line temperatures shown in Table 1, in an inert atmospherefor 20 hours. After being heat treated, the material is ground with aball mill, and classified using a sieve to prepare composite particlesof 45 μm or less. An electron microscope observation confirmed, thesecomposite particles have part of or the whole surface of the solid phaseA thereof covered with the solid phase B.

The construction of the battery of the present invention is describedbelow taking an example of a cylindrical battery according to preferredembodiments.

The First Preferred Embodiment

FIG. 1 shows a vertical cross section of a cylindrical battery of thepresent invention. In FIG. 1, a positive electrode plate 5 and anegative electrode plate 6 are spirally rolled a plurality of times viaseparators 7, and placed in a battery casing 1. Coming out from thepositive electrode plate 5 is a positive electrode lead 5 a, which isconnected to a sealing plate 2. In the same manner, a negative electrodelead 6 a comes out from a negative electrode plate 6, and is connectedto the bottom of the battery casing 1. Insulating gasket 3 separatessealing plate 2 from battery casing 1.

Electronally conductive metals and alloys having organic electrolyticsolution resistance can be used for the battery casing and lead plates.For example, such metals as iron, nickel, titanium, chromium,molybdenum, copper and aluminum and their alloys can be used. For thebattery casing, stainless steel plate or processed Al—Mn alloy plate isfavorably used, and for the positive electrode lead and the negativeelectrode lead, respectively aluminum and nickel are most favorable. Forthe battery casing, engineering plastics can be used independently orwith metals in order to reduce weight.

Insulating rings 8 are disposed on the top and bottom of an electrodeplate group 4. A safety valve can be used as a sealing plate. Apart fromthe safety valve, other conventionally used safety elements can bedisposed. As an anti-overcurrent element, for example, fuses, bimetaland PTC elements can be used. To deal with increases in internalpressure of the battery casing, a cut can be provided to the batterycasing, a gasket cracking method or a sealing plate cracking method canbe applied, or the connection to the lead plate can be severed. As othermethods, a protective circuit incorporating anti-overcharging andanti-overdischarging systems, can be included in or connectedindependently to a charger. As an anti-overcharging method, current canbe cut off by an increase in internal pressure of the battery. In thiscase, a compound which increases internal pressure can be mixed with theelectrode mixture or with the electrolytes. Such compounds includecarbonates such as Li₂CO₃, LiHCO₃, Na₂CO₃, NaHCO₃, CaCO₃ and MgCO_(3.)

The cap, the battery casing, the sheet and the lead plate can be weldedby conventional methods such as an alternative current or a directcurrent electric welding, a laser welding and an ultrasonic welding. Asa sealing material, conventional compounds and composites such asasphalt can be used.

To prepare the negative electrode plate 6, 20 wt % of carbon powder and5 wt % PVDF are mixed with 75 wt % of the composite particlessynthesized under the foregoing conditions. The mixture is dispersed indehydrated. N-methyl pyrrolidone to form a slurry. The slurry is coatedonto a negative electrode current collector comprising copper foil,dried and rolled under pressure.

To prepare the positive electrode plate 5, 10 wt % of carbon powder and5 wt % of PVDF are mixed with 85 wt % of lithium cobaltate powder. Themixture is dispersed in dehydrated N-methyl pyrrolidinone to form aslurry. The slurry is coated onto a positive electrode current collectorcomprising copper foil, and dried and rolled under pressure.

1.5 mol/l of (C₂F₅SO₂)₂NLi is dissolved in a mixed solvent of EC and EMCwhich are mixed in a ratio of 1:1 by volume, and used as an electrolyte.

In the foregoing manner, batteries are constructed by using thematerials shown in Table 1 for the negative electrode. These cylindricalbatteries are 18 mm in diameter and 65 mm in height. The batteries arecharged at a constant current of 100 mA until their voltage becomes4.1V, and then discharged at a constant current of 100 mA until theirvoltage becomes 2.0V. The charge/discharge cycle is repeated 100 times,and the ratio of the discharge capacity at the 100th cycle to that ofthe first cycle is shown in Table 2 as the capacity retention rate. Forcomparison, results of batteries using graphite or an Al—Li alloy fornegative electrodes are shown in Table 2.

Table 2 also shows capacity retention rates obtained by comparing theinitial capacity measured when the batteries of the same constructionare charged at the constant current of 100 mA until their voltagebecomes 4.1V and discharged at the constant current of 100 mA untiltheir voltage becomes 2.0V, and the capacity measured when the samebatteries are charged again under the same conditions until theirvoltage becomes 4.1V and stored for 20 days at 60° C. The capacityretention rate is a ratio of the discharge capacities after storage tobefore storage. After storing, a hole is made on the battery and gas iscollected in liquid paraffin. The amount of the collected gas is shownas a ratio against the amount of gas (=100) produced by a battery usinggraphite in the negative electrode.

The Second Preferred Embodiment

Batteries are prepared using PC as a solvent of the electrolyte anddissolving 1.0 mol/l of bis(5-fluoro-2-olate-1-benzene sulfonicacid-O,O′)lithium borate as a supporting electrolyte. Besides thesepoints, batteries are formed and tests are conducted in the same manneras the first embodiment. Results are shown in Table 3.

The Third Preferred Embodiment

Batteries are prepared using GBL as a solvent of the electrolyte anddissolving 1.2 mol/l of bis(2,2′-biphenyl diolate(2-)-O,O′)lithiumborate as a supporting electrolyte. In all other respects, batteries areformed and tests are conducted in the same manner as the firstembodiment. Results are shown in Table 4.

The Fourth Preferred Embodiment

Batteries are prepared in the following manner. As a positive electrodecurrent collector, titanium foil of 0.02 mm in thickness is used. EC,DMC and DEC are mixed together at a ratio of 2:3:3 by volume and used asa mixed solvent of the electrolyte. 1.2 mol/l of (CF₃SO₂)₂NLi isdissolved in the electrolyte as a supporting electrolyte. Apart from theforegoing points, batteries are formed and tests are conducted in thesame manner as the first embodiment. Results are shown in Table 5.

The Fifth Preferred Embodiment

Batteries are prepared using LiTiS₂ as a positive electrode material,and gamma-valerolactone as a solvent of the electrolytic solution. 1.2mol/l of bis(1,2-benzene diolate(2-)-O,O′)lithium borate is dissolved inthe electrolyte as a supporting electrolyte. Apart from the foregoingpoints, batteries are formed and tests are conducted in the same manneras the first embodiment. The batteries are charged at the constantcurrent of 100 mA until their voltage becomes 2.8V, and then dischargedat the constant current of 100 mA until their voltage becomes 0.5V. Thecharge/discharge cycle is repeated 100 times, and ratio of the dischargecapacity at the 100th cycle to that of the first cycle is shown in Table6 as the capacity retention rate. Table 6 also shows capacity retentionrates gained by comparing the initial capacity measured when thebatteries of the same construction are charged at the constant currentof 100 mA until their voltage becomes 2.8V and discharged at theconstant current of 100 mA until their voltage becomes 0.5V, and thecapacity measured when the same batteries are charged again on the samecondition until their voltage becomes 2.8V and stored for 20 days at 60°C. The amount of gas collected in liquid paraffin is shown in Table 6 aswell.

The Sixth Preferred Embodiment

Batteries are prepared in the following manner. LiTiS₂ is used as apositive electrode material. EC and DEC are mixed together at a ratio of1:2 by volume and used as a, mixed solvent of the electrolyte. 1.0 mol/lof bis(2,3-naphthalene diolate(2-)-O,O′)lithium borate is dissolved as asupporting electrolyte. Apart from the foregoing points, batteries areformed in the same manner as the first embodiment. These batteries aretested using the same method as that of the fifth preferred embodiment.Results are shown in Table 7.

As shown in Tables 2-7, the batteries of the present invention have ahigher energy density and enjoy the same level of cycle capacityretention rate compared with the conventional batteries which usegraphite as the negative electrode. Furthermore, the batteries of thepresent invention produce lesser amounts of gas than the conventionalbatteries when fully charged and stored at high temperatures.

Regarding constituent elements of the negative electrode materials, whenthe solid phase A is Sn, Mg selected from group 2 elements, Fe and Mofrom transition elements, Zn and Cd from group 12 elements, In fromgroup 13 elements and Pb from group 14 elements are used. However,similar results are obtained with other elements selected from eachgroup. The composition ratio of the constituent elements of the negativeelectrode material is not specifically defined, on the condition thattwo phases are created and one of which (solid phase A) is mainlycomposed of Sn, and partly or entirely covered with the other phase(solid phase B). The solid phase A can be composed not only of Sn butalso traces of other elements such as O, C, N, S, Ca, Mg, Al, Fe, W, V,Ti, Cu, Cr, Co, and P.

When the solid phase A is Si, Mg selected from group 2 elements, Co andNi from transition elements, Zn from group 12 elements, Al from group 13elements and Sn from group 14 elements are used. However, similarresults are obtained with other elements selected from each group.Similarly, when the solid phase A is Zn, Mg from group 2 elements, Cuand V from transition elements, Cd from group 12 elements, Al from group13 elements and Ge from group 14 elements are used. However, similarresults are obtained with other elements selected from each group. Thecomposition ratio of the constituent elements of the negative electrodematerial is not specifically defined, on the condition that two phasesare created and one of which (solid phase A) is mainly composed of Siand Zn, and partly or entirely covered with the other phase (solid phaseB). The solid phase A can be composed not only of Si and Zn but alsotraces of elements such as O, C, N, S, Ca, Mg, Al, Fe, W, V, Ti, Cu, Cr,Co, and P.

It is to be understood that the foregoing combinations and mixtureratios of the electrolytes, the materials for the supportingelectrolytes, and the amount added constitute only part of the presentinvention. Depending on conditions for use and other necessary elements,any combination, mixture ratio and the amount to be added can be appliedwith similar results. Thus, the electrolytes of the present inventionare not limited to the combination, mixture ratio and the amount to beadded described in the preferred embodiments. However, depending on thepositive electrode materials, specified supporting electrolytes arerequired due to the oxidation resistance voltages.

The battery of the present invention can be used for portableinformation terminals, portable electronic devices, small size domesticelectricity storing devices, motor cycles, electric cars and hybridelectric cars. However, the application of the battery is not limited tothe foregoing.

APPLICABILITY IN THE INDUSTRY

A non-aqueous electrolyte secondary battery using the non-aqueouselectrolyte and the composite particles according to the presentinvention shows high energy density compared with conventional one whichuses carbon materials as a negative electrode material. It also shows animproved charge/discharge cycle life characteristics. As such, thebatteries of the present invention can be used in portable informationterminals, portable electronic devices, domestic portable electricitystoring devices, motor cycles, electric cars and hybrid electric cars,thereby offering remarkable benefits when industrially applied.

TABLE 1 Solid phase Melting line Negative temper- temper- electrodePhase ature ature Composition material A Phase B (° C.) (° C.) (Atom %)Material A Sn Mg₂Sn 770 204 Sn:Mg = 50:50 Material B Sn FeSn₂ 1540 513Sn:Fe = 70:30 Material C Sn MoSn₂ 1200 800 Sn:Mo = 70:30 Material D SnZn, 420 199 Sn:Zn = 90:10 Sn Solid S. Material E Sn Cd, 232 133 Sn:Cd =95:5 Sn Solid S. Material F Sn In, 235 224 Sn:In = 98:2 Sn Solid S.Material G Sn Sn, 232 183 Sn:Pb = 80:20 Pb Solid S. Material H Si Mg₂Si1415 946 Si:Mg = 70:30 Material I Si CoSi₂ 1495 1259 Si:Co = 85:15Material J Si NiSi₂ 1415 993 Si:Ni = 69:31 Material K Si Si, 1415 420Si:Zn = 50:50 Zn Solid S. Material L Si Si, 1415 577 Si:Al = 40:60 AlSolid S. Material M Si Si, 1415 232 Si:Sn = 50:50 Sn Solid S. Material NZn Mg₂Zn₁₁ 650 364 Zn:Mg = 92.9:7.8 Material O Zn Zn, 1085 425 Zn:Cu =97:3 Cu Solid S. Material P Zn VZn₁₁ 700 420 Zn:V = 94:6 Material Q ZnZn, 420 266 Zn:Cd = 50:50 Cd Solid S. Material R Zn Zn, 661 381 Zn:Al =90:10 Al Solid S. Material S Zn Zn, 938 394 Zn:Ge = 97:3 Ge Solid S.

TABLE 2 Initial 100th Capacity Capacity Negative Discharge Dischargeretention rate retention rate Gas generation electrode Capacity Capacity(cycle) (%) rate (%) Battery material (mAh) (mAh) (%) (storing)(storing) 1 Material 1882 1731 92 90 82 A 2 B 1874 1705 91 91 81 3 C1857 1671 90 89 84 4 D 1862 1713 92 92 80 5 E 1885 1753 90 90 82 6 F1871 1740 93 88 83 7 G 1881 1731 92 89 84 8 H 1966 1809 92 90 78 9 I1950 1775 91 91 75 10 J 1984 1845 93 91 73 11 K 1979 1821 92 90 73 12 L1999 1799 90 89 72 13 M 1991 1832 92 89 74 14 N 1949 1813 93 90 79 15 O1955 1799 92 91 81 16 P 1911 1739 91 92 82 17 Q 1920 1766 92 92 78 18 R1959 1802 92 89 80 19 S 1917 1744 91 91 77 20 graphite 1520 1429 94 83100 21 Al—Li 1876 1632 87 80 112 alloy

TABLE 3 Initial 100th Capacity Capacity Negative Discharge Dischargeretention rate retention rate Gas generation electrode Capacity Capacity(cycle) (%) rate (%) Battery material (mAh) (mAh) (%) (storing)(storing) 1 Material 1887 1717 91 92 82 A 2 B 1879 1691 90 93 79 3 C1862 1657 89 91 80 4 D 1867 1699 91 94 79 5 E 1890 1739 92 92 82 6 F1876 1726 92 90 80 7 G 1886 1716 91 91 79 8 H 1971 1794 91 92 74 9 I1955 1760 90 93 72 10 J 1989 1830 92 92 71 11 K 1984 1825 92 92 71 12 L2004 1824 91 91 69 13 M 1996 1816 91 90 70 14 N 1954 1798 92 90 77 15 O1960 1803 92 92 82 16 P 1916 1724 90 94 81 17 Q 1925 1752 91 94 79 18 R1964 1807 92 91 78 19 S 1922 1749 91 93 76 20 graphite 1525 1418 85 85100 21 Al—Li 1881 1599 85 82 118 alloy

TABLE 4 Initial 100th Capacity Capacity Negative Discharge Dischargeretention rate retention rate Gas generation electrode Capacity Capacity(cycle) (%) rate (%) Battery material (mAh) (mAh) (%) (storing)(storing) 1 Material 1880 1692 90 90 80 A 2 B 1872 1704 91 91 79 3 C1855 1632 88 92 78 4 D 1860 1674 90 93 77 5 E 1883 1714 91 92 79 6 F1869 1719 92 91 77 7 G 1879 1729 92 92 76 8 H 1964 1787 91 90 71 9 I1948 1797 92 92 70 10 J 1982 1784 90 92 69 11 K 1977 1799 91 91 69 12 L1997 1797 90 91 67 13 M 1989 1830 92 91 68 14 N 1947 1752 90 92 75 15 O1953 1777 91 93 80 16 P 1909 1737 91 95 79 17 Q 1918 1726 90 93 77 18 R1957 1800 92 92 76 19 S 1915 1743 91 94 74 20 graphite 1518 1397 92 84100 21 Al—Li 1874 1555 83 83 120 alloy

TABLE 5 Initial 100th Capacity Capacity Negative Discharge Dischargeretention rate retention rate Gas generation electrode Capacity Capacity(cycle) (%) rate (%) Battery material (mAh) (mAh) (%) (storing)(storing) 1 Material 1877 1708 91 91 77 A 2 B 1869 1682 90 90 71 3 C1852 1648 89 91 75 4 D 1857 1690 91 92 73 5 E 1880 1730 92 93 77 6 F1866 1717 92 91 76 7 G 1876 1707 91 92 75 8 H 1961 1785 91 90 69 9 I1945 1751 90 91 70 10 J 1979 1821 92 92 67 11 K 1974 1816 92 93 66 12 L1994 1815 91 90 63 13 M 1986 1807 91 91 66 14 N 1944 1788 92 92 74 15 O1950 1794 92 91 80 16 P 1906 1715 90 93 77 17 Q 1915 1743 91 92 75 18 R1954 1798 92 90 74 19 S 1912 1740 91 91 73 20 graphite 1515 1409 93 83100 21 Al—Li 1871 1590 85 79 123 alloy

TABLE 6 Initial 100th Capacity Capacity Negative Discharge Dischargeretention rate retention rate Gas generation electrode Capacity Capacity(cycle) (%) rate (%) Battery material (mAh) (mAh) (%) (storing)(storing) 1 Material 2820 2538 90 91 79 A 2 B 2808 2499 89 93 77 3 C2783 2499 88 92 76 4 D 2790 2539 91 91 76 5 E 2825 2571 91 92 74 6 F2804 2552 91 90 75 7 G 2819 2593 92 91 72 8 H 2946 2740 93 91 72 9 I2922 2688 92 93 73 10 J 2973 2646 89 92 70 11 K 2966 2699 91 90 71 12 L2996 2756 92 91 69 13 M 2984 2715 91 92 68 14 N 2921 2687 92 93 73 15 O2930 2666 91 90 79 16 P 2864 2578 90 92 79 17 Q 2877 2676 93 91 77 18 R2936 2613 89 93 76 19 S 2873 2614 91 92 73 20 graphite 2277 2049 90 82100 21 Al—Li 2811 2333 83 83 122 alloy

TABLE 7 Initial 100th Capacity Capacity Negative Discharge Dischargeretention rate retention rate Gas generation electrode Capacity Capacity(cycle) (%) rate (%) Battery material (mAh) (mAh) (%) (storing)(storing) 1 Material 2726 2426 89 89 78 A 2 B 2714 2443 90 90 76 3 C2690 2340 87 90 77 4 D 2697 2400 89 91 77 5 E 2730 2454 90 90 76 6 F2710 2466 91 89 74 7 G 2725 2480 91 90 73 8 H 2848 2563 90 92 70 9 I2825 2563 91 91 71 10 J 2874 2558 89 92 70 11 K 2867 2580 90 91 68 12 L2896 2577 89 93 68 13 M 2884 2624 91 91 69 14 N 2823 2484 88 89 74 15 O2832 2520 89 93 79 16 P 2768 2491 90 92 76 17 Q 2781 2503 90 93 77 18 R2838 2583 91 90 75 19 S 2777 2472 89 94 73 20 graphite 2201 1937 88 80100 21 Al—Li 2717 2255 83 80 128 alloy

What is claimed is:
 1. A non-aqueous electrolyte secondary batterycomprising: a positive electrode, a negative electrode capable ofintercalating and de-intercalating lithium, a non-aqueous electrolytesolution, and a separator or a solid electrolyte, wherein: said negativeelectrode comprises composite particles, each of said compositeparticles comprises a nuclear particle consisting essentially of anelement selected from the group consisting of tin, silicon, and zinc, atleast a part of a surface of said nuclear particles is coated witheither a solid solution or an inter-metallic compound, said solidsolution or intermetallic compound comprises said element selected fromthe group consisting of tin, silicon, and zinc and at least oneadditional element, said additional element selected from the groupconsisting of group 2 elements, transition elements, group 12 elements,group 13 elements and group 14 elements exclusive of carbon, andexclusive of said element selected from the group consisting of tin,silicon, and zinc, and said non-aqueous electrolyte solution comprisesan organic solvent and a lithium salt of an organic acid.
 2. Thenon-aqueous electrolyte secondary battery of claim 1, wherein saidorganic solvent comprises at least one compound selected from the groupconsisting of ethylene carbonate, dimethyl carbonate, diethyl carbonate,ethylmethyl carbonate, propylene carbonate, gamma-butyro lactone, andgamma-valero lactone.
 3. The non-aqueous electrolyte secondary batteryof claim 1, wherein said lithium salt of said organic acid is at leastone compound selected from the group consisting bis-trifluoromethanesulfonic acid imido lithium, bis-pentafluoroethane sulfonic acid imidolithium, bis(1,2-benzene diolate(2-)-O,O′)lithium borate,bis(2,3-naphthalene diolate(2-)-O,O′)lithium borate, bis(2,2′-biphenyldiolate(2-)-O,O′)lithium borate, andbis(5-fluoro-2-olate-1-benzene-sulfonic acid-O,O′)lithium borate.
 4. Thenon-aqueous electrolyte secondary battery of claim 1, wherein saidelement selected from the group consisting of tin, silicon, and zinc istin.
 5. The non-aqueous electrolyte secondary battery of claim 1,wherein said element selected from the group consisting of tin, silicon,and zinc is silicon.
 6. The non-aqueous electrolyte secondary battery ofclaim 1, wherein said element selected from the group consisting of tin,silicon, and zinc is zinc.
 7. The non-aqueous electrolyte secondarybattery of claim 1, wherein said additional element is selected from thegroup consisting of Mg, Fe, Mo, Zn, Cd, In, Pb, Co, Ni, Al, Sn, Cu, V,and Ge; and wherein when said element selected from the group consistingof tin, silicon, and zinc is tin, said additional element is not tin,and when said element selected from the group consisting of tin,silicon, and zinc is zinc, said additional element is not zinc.
 8. Anon-aqueous electrolyte secondary battery comprising: a positiveelectrode, a negative electrode capable of intercalating andde-intercalating lithium, a non-aqueous electrolyte solution, and aseparator or a solid electrolyte, wherein: said negative electrodecomprises composite particles, each of said composite particlescomprises a nuclear particle comprising silicon, at least a part of asurface of said nuclear particles is coated with either a solid solutionor an inter-metallic compound, said solid solution or intermetalliccompound comprises silicon and at least one additional element, saidadditional element selected from the group consisting of group 2elements, transition elements, group 12 elements, group 13 elements andgroup 14 elements exclusive of carbon and silicon, and said non-aqueouselectrolyte solution comprises an organic solvent and a lithium salt ofan organic acid.
 9. The non-aqueous electrolyte secondary battery ofclaim 8, wherein said organic solvent comprises at least one compoundselected from the group consisting of ethylene carbonate, dimethylcarbonate, diethyl carbonate, ethylmethyl carbonate, propylenecarbonate, gamma-butyro lactone, and gamma-valero lactone.
 10. Thenon-aqueous electrolyte secondary battery of claim 8, wherein saidlithium salt of said organic acid is at least one compound selected fromthe group consisting bis-trifluoromethane sulfonic acid imido lithium,bis-pentafluoroethane sulfonic acid imido lithium, bis(1,2-benzenediolate(2-)-O,O′)lithium borate, bis(2,3-naphthalenediolate(2-)-O,O′)lithium borate, bis(2,2′-biphenyldiolate(2-)-O,O′)lithium borate, andbis(5-fluoro-2-olate-1-benzene-sulfonic acid-O,O′)lithium borate. 11.The non-aqueous electrolyte secondary battery of claim 8, wherein saidadditional element is selected from the group consisting of Mg, Co, Ni,Zn, Al, and Sn.